Impact of compost, manure and inorganic fertilizer on nitrate leaching and yield for a 6-year maize-alfalfa rotation in Michigan [An article from: Agriculture, Ecosystems and Environment]

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An accurate estimate of nitrate (NO"3?N) leaching from agricultural land is critical to environment impact studies. Although NO"3?N are almost always present in groundwater, their continued increase in managed agricultural land can lead to nitrate concentrations in groundwater above acceptable human health standards. The amount of NO"3?N leached during the growing season may be minimal compared to leaching losses that occur between the harvest of one crop and the planting of the next. In this study we compared the effect of inorganic N and raw and composted animal manure on crop productivity and N leaching under field conditions in a maize-alfalfa system using undisturbed drainage lysimeters in Michigan. The cropping system rotation consisted of 3 years of continuous maize (Zea mays L.) and 3 years of continuous alfalfa (Medicago sativa L.). One cropping system consisted of a maize crop grown in the 1994-1996 seasons and alfalfa in the 1997-1999 seasons. The other cropping system was alfalfa (1994-1996) then maize (1997-1999). Four N treatments were imposed on the cropping systems. Treatment 1 was a check, no N fertilizer; Treatment 2 was manure; Treatment 3 was compost; Treatment 4 was inorganic fertilizer. No significant differences in yields of maize and alfalfa were found between N treatments in the 6-year rotation, although the no N treatment in maize had consistently lower yields. The highest amount of NO"3?N leaching was measured in the manure treatment with a mean annual value of 55kg NO"3?Nha^-^1 in maize-alfalfa rotation and 59kg NO"3?Nha^-^1 in alfalfa-maize, followed by compost (35kg NO"3?Nha^-^1 in alfalfa-maize and 30kg NO"3?Nha^-^1 in maize-alfalfa), inorganic N (33kg NO"3?Nha^-^1 in alfalfa-maize and 25kg NO"3?Nha^-^1 in maize-alfalfa) and no N (27kg NO"3?Nha^-^1 in alfalfa-maize and 25kg NO"3?Nha^-^1 in maize-alfalfa). The highest rates of NO"3?N losses were also observed in the manure treatment with a mean value for the 6-year rotation of 0.14kg NO"3?Nmm^-^1 in alfalfa-maize and 0.35kg NO"3?Nmm^-^1 in maize-alfalfa.